Multi-pronged approach to constrain the age of the Molopo Farms layered igneous complex, Northern Cape Province and Southeastern Botswana
- Authors: Ravhura, Livhuwani Given
- Date: 2016
- Subjects: Geochronology , Geology - Botswana , Geology - South Africa - Northern Cape , Igneous rocks - Botswana , Igneous rocks - South Africa - Northern Cape , Molopo Farms Complex (Botswana and South Africa)
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/235897 , uj:24133
- Description: M.Sc. (Geology) , Abstract: This study presents the first detailed major- and trace element geochemical and geochronological studies of the Molopo Farms Complex (MFC), situated in the Northern Cape Province, South Africa and south eastern Botswana. The rocks of the MFC are gabbro, serpentinite, pyroxenite and intrudes into sedimentary host rocks, these rocks are medium- to coarse grained. The mafic igneous rocks of the MFC are dominantly sub-alkaline tholeiitic in composition and characterized as basaltic andesite. The MFC is completely covered by Cenozoic sediments of the Kalahari Formation and it is only known through intersection in exploration drill core and geophysical data. It is thought that the MFC has intruded the sedimentary succession of the Paleoproterozoic Transvaal Supergroup. Unlike other layered complexes (Bushveld Complex, Stillwater Complex, etc.), no detailed geochemical studies have been done on the MFC. At present, the available age is the poorly constrained at 2044±24 Ma (Rb-Sr errorchron age) and for that reason, and the fact that it is a layered igneous complex it has been correlated with Bushveld Complex. However, this age and correlation are poorly constrained. This study provides additional data on the geochemical composition of the igneous rocks to fully understand the geochemical signature of the igneous rocks of the MFC, a baddeleyite age on a gabbro from the complex and also detrital zircon age data on the sedimentary country rocks. The geochemical signature of the MFC has been compared to that of other magmatic events (Bushveld Complex, Moshaneng dykes and Post Waterberg sills) to evaluate the similarities in composition. The MFC is characterized by an enrichment in LREE relative to the HREE and shows negative Eu, Nb(Ta), P, Ti and positive K, Pb and U anomalies. This geochemical signature compares well with that of the B1-magma of the Bushveld Complex. An age of 2052±16 Ma, obtained from U-Pb baddeleyite dating, has been interpreted to be the emplacement age of the MFC. This age is within error with the 2054.4±1.3 Ma accepted age of the Bushveld Complex. The maximum age of sedimentary country rock into which MFC intrudes has been better constrained by U-Pb detrital zircon dating. The youngest concordant zircon ages obtained are between 2018±39 and...
- Full Text:
- Authors: Ravhura, Livhuwani Given
- Date: 2016
- Subjects: Geochronology , Geology - Botswana , Geology - South Africa - Northern Cape , Igneous rocks - Botswana , Igneous rocks - South Africa - Northern Cape , Molopo Farms Complex (Botswana and South Africa)
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/235897 , uj:24133
- Description: M.Sc. (Geology) , Abstract: This study presents the first detailed major- and trace element geochemical and geochronological studies of the Molopo Farms Complex (MFC), situated in the Northern Cape Province, South Africa and south eastern Botswana. The rocks of the MFC are gabbro, serpentinite, pyroxenite and intrudes into sedimentary host rocks, these rocks are medium- to coarse grained. The mafic igneous rocks of the MFC are dominantly sub-alkaline tholeiitic in composition and characterized as basaltic andesite. The MFC is completely covered by Cenozoic sediments of the Kalahari Formation and it is only known through intersection in exploration drill core and geophysical data. It is thought that the MFC has intruded the sedimentary succession of the Paleoproterozoic Transvaal Supergroup. Unlike other layered complexes (Bushveld Complex, Stillwater Complex, etc.), no detailed geochemical studies have been done on the MFC. At present, the available age is the poorly constrained at 2044±24 Ma (Rb-Sr errorchron age) and for that reason, and the fact that it is a layered igneous complex it has been correlated with Bushveld Complex. However, this age and correlation are poorly constrained. This study provides additional data on the geochemical composition of the igneous rocks to fully understand the geochemical signature of the igneous rocks of the MFC, a baddeleyite age on a gabbro from the complex and also detrital zircon age data on the sedimentary country rocks. The geochemical signature of the MFC has been compared to that of other magmatic events (Bushveld Complex, Moshaneng dykes and Post Waterberg sills) to evaluate the similarities in composition. The MFC is characterized by an enrichment in LREE relative to the HREE and shows negative Eu, Nb(Ta), P, Ti and positive K, Pb and U anomalies. This geochemical signature compares well with that of the B1-magma of the Bushveld Complex. An age of 2052±16 Ma, obtained from U-Pb baddeleyite dating, has been interpreted to be the emplacement age of the MFC. This age is within error with the 2054.4±1.3 Ma accepted age of the Bushveld Complex. The maximum age of sedimentary country rock into which MFC intrudes has been better constrained by U-Pb detrital zircon dating. The youngest concordant zircon ages obtained are between 2018±39 and...
- Full Text:
Petrography and geochemistry of the Hotazel Formation on Mukulu 265, Kalahari Manganese Field, Northern Cape Province
- Authors: Vafeas, Nicholas Andrew
- Date: 2016
- Subjects: Geology - South Africa - Northern Cape , Manganese ores - Kalahari Desert , Iron ores
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/124793 , uj:20960
- Description: Abstract: With the need for steel ever increasing, the Kalahari Manganese Deposit is a resource of great economic importance and as such, the need for accurate data and comprehensive studies on the manganese and iron ores are vital. The Mukulu 265 project area is positioned along the border of the high (Wessels-type) to low (Mamatwan-type) grade manganese ore and like the neighbouring N’chwaning and Wessels mines, is subject to: intrusions by diabase dykes; thrusting and subsequent overlapping of strata; normal faulting and associated Wessels event enrichment; and erosion along two separate unconformities, namely the Mapedi/Gamagara and the Kalahari unconformities. As a result of these structural evolutionary events, both the iron and the manganese ores vary in grade, mineralogy and texture from north to south and east to west. This variation is the result of contact metamorphism and associated igneousrelated hydrothermal fluids; supergene alteration along the Mapedi/Gamagara unconformity; and metasomatic alteration along the reactivated north-south striking normal faults. The latter is responsible for the systematic residual enrichment in manganese content and the increase in high-grade minerals in the manganese ore, as well as the subsequent leaching of carbonates and silicates that is witnessed in the northern section of Mukulu 265. Based on varying degrees of alteration from south to north on Mukulu 265, the banded iron formation, hematite lutite and manganese ores have been broadly categorised into three classes, namely least altered (LA), partially altered (PA) and highly altered (HA). The LA rock-types are considered to be closest to the primary rock-types found on Mukulu 265 and show relatively little alteration compared to the PA and HA samples. From the LA to the HA manganese ore samples, there is a clear increase in manganese oxides such as hausmannite, predominantly at the expense of carbonates such and kutnohorite and dolomite, particularly within the ovoids. Sampling and analysing the manganese ore by visually distinguishing common subzones, reveals a distinct pattern within the lower manganese ore beds of the selected boreholes that shows a lateral geochemical trend. This geochemical trend exhibits higher concentrations in manganese with lower concentrations in undesired elements such as iron within the lowercentral portion of the lower manganese ore bed. The geochemical pattern exhibited by the ore zones forms the basis by which the ore grade changes with depth and thus underpins its importance for selective mining processes. An interpretation of the ore genesis based on geochemical and mineralogical results for the lower manganese ore bed, suggests that the... , M.Sc. (Geology)
- Full Text:
- Authors: Vafeas, Nicholas Andrew
- Date: 2016
- Subjects: Geology - South Africa - Northern Cape , Manganese ores - Kalahari Desert , Iron ores
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/124793 , uj:20960
- Description: Abstract: With the need for steel ever increasing, the Kalahari Manganese Deposit is a resource of great economic importance and as such, the need for accurate data and comprehensive studies on the manganese and iron ores are vital. The Mukulu 265 project area is positioned along the border of the high (Wessels-type) to low (Mamatwan-type) grade manganese ore and like the neighbouring N’chwaning and Wessels mines, is subject to: intrusions by diabase dykes; thrusting and subsequent overlapping of strata; normal faulting and associated Wessels event enrichment; and erosion along two separate unconformities, namely the Mapedi/Gamagara and the Kalahari unconformities. As a result of these structural evolutionary events, both the iron and the manganese ores vary in grade, mineralogy and texture from north to south and east to west. This variation is the result of contact metamorphism and associated igneousrelated hydrothermal fluids; supergene alteration along the Mapedi/Gamagara unconformity; and metasomatic alteration along the reactivated north-south striking normal faults. The latter is responsible for the systematic residual enrichment in manganese content and the increase in high-grade minerals in the manganese ore, as well as the subsequent leaching of carbonates and silicates that is witnessed in the northern section of Mukulu 265. Based on varying degrees of alteration from south to north on Mukulu 265, the banded iron formation, hematite lutite and manganese ores have been broadly categorised into three classes, namely least altered (LA), partially altered (PA) and highly altered (HA). The LA rock-types are considered to be closest to the primary rock-types found on Mukulu 265 and show relatively little alteration compared to the PA and HA samples. From the LA to the HA manganese ore samples, there is a clear increase in manganese oxides such as hausmannite, predominantly at the expense of carbonates such and kutnohorite and dolomite, particularly within the ovoids. Sampling and analysing the manganese ore by visually distinguishing common subzones, reveals a distinct pattern within the lower manganese ore beds of the selected boreholes that shows a lateral geochemical trend. This geochemical trend exhibits higher concentrations in manganese with lower concentrations in undesired elements such as iron within the lowercentral portion of the lower manganese ore bed. The geochemical pattern exhibited by the ore zones forms the basis by which the ore grade changes with depth and thus underpins its importance for selective mining processes. An interpretation of the ore genesis based on geochemical and mineralogical results for the lower manganese ore bed, suggests that the... , M.Sc. (Geology)
- Full Text:
- «
- ‹
- 1
- ›
- »